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B Monoecious plants like castor and maize prevent both autogamy and geitonogamy.
Transfer of pollen grains from the anther to the stigma of the same flower is called self-pollination or autogamy.
If the pollen grains are transferred between the flowers of the same plant, this type of pollination is called geitonogamy.
In monoecious plants like castor and maize which have both male and female flowers present on the same plant, they prevent autogamy but not geitonogamy.
In wind pollinated flowers, the pollen grains are light and non -sticky so that they can be easily transported by wind currents.
Chalaza represents the basal part of the ovule which is opposite the micropylar end.
Pollen grains are well preserved as fossils because of the presence of sporopollenin. This is because sporopollenin is a highly resistant substance and cannot be degraded by any enzymes, strong acids, alkali or even high temperatures.